From: Stefano Garzarella Date: Thu, 3 Apr 2025 10:09:39 +0000 (+0200) Subject: x86/sev: Add SVSM vTPM probe/send_command functions X-Git-Tag: v6.16-rc1~179^2~3 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=770de678bc281f6b0be339c29c1ad74dfb0e9325;p=linux-block.git x86/sev: Add SVSM vTPM probe/send_command functions Add two new functions to probe and send commands to the SVSM vTPM. They leverage the two calls defined by the AMD SVSM specification [1] for the vTPM protocol: SVSM_VTPM_QUERY and SVSM_VTPM_CMD. Expose snp_svsm_vtpm_send_command() to be used by a TPM driver. [1] "Secure VM Service Module for SEV-SNP Guests" Publication # 58019 Revision: 1.00 [ bp: Some doc touchups. ] Co-developed-by: James Bottomley Signed-off-by: James Bottomley Co-developed-by: Claudio Carvalho Signed-off-by: Claudio Carvalho Signed-off-by: Stefano Garzarella Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Tom Lendacky Reviewed-by: Jarkko Sakkinen Link: https://lore.kernel.org/r/20250403100943.120738-2-sgarzare@redhat.com --- diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c index b0c1a7a57497..ecd09dad87f2 100644 --- a/arch/x86/coco/sev/core.c +++ b/arch/x86/coco/sev/core.c @@ -2625,6 +2625,64 @@ e_restore_irq: return ret; } +/** + * snp_svsm_vtpm_probe() - Probe if SVSM provides a vTPM device + * + * Check that there is SVSM and that it supports at least TPM_SEND_COMMAND + * which is the only request used so far. + * + * Return: true if the platform provides a vTPM SVSM device, false otherwise. + */ +static bool snp_svsm_vtpm_probe(void) +{ + struct svsm_call call = {}; + + /* The vTPM device is available only if a SVSM is present */ + if (!snp_vmpl) + return false; + + call.caa = svsm_get_caa(); + call.rax = SVSM_VTPM_CALL(SVSM_VTPM_QUERY); + + if (svsm_perform_call_protocol(&call)) + return false; + + /* Check platform commands contains TPM_SEND_COMMAND - platform command 8 */ + return call.rcx_out & BIT_ULL(8); +} + +/** + * snp_svsm_vtpm_send_command() - Execute a vTPM operation on SVSM + * @buffer: A buffer used to both send the command and receive the response. + * + * Execute a SVSM_VTPM_CMD call as defined by + * "Secure VM Service Module for SEV-SNP Guests" Publication # 58019 Revision: 1.00 + * + * All command request/response buffers have a common structure as specified by + * the following table: + * Byte Size     In/Out    Description + * Offset    (Bytes) + * 0x000     4          In        Platform command + *                         Out       Platform command response size + * + * Each command can build upon this common request/response structure to create + * a structure specific to the command. See include/linux/tpm_svsm.h for more + * details. + * + * Return: 0 on success, -errno on failure + */ +int snp_svsm_vtpm_send_command(u8 *buffer) +{ + struct svsm_call call = {}; + + call.caa = svsm_get_caa(); + call.rax = SVSM_VTPM_CALL(SVSM_VTPM_CMD); + call.rcx = __pa(buffer); + + return svsm_perform_call_protocol(&call); +} +EXPORT_SYMBOL_GPL(snp_svsm_vtpm_send_command); + static struct platform_device sev_guest_device = { .name = "sev-guest", .id = -1, diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h index ba7999f66abe..d9ba035d8609 100644 --- a/arch/x86/include/asm/sev.h +++ b/arch/x86/include/asm/sev.h @@ -384,6 +384,10 @@ struct svsm_call { #define SVSM_ATTEST_SERVICES 0 #define SVSM_ATTEST_SINGLE_SERVICE 1 +#define SVSM_VTPM_CALL(x) ((2ULL << 32) | (x)) +#define SVSM_VTPM_QUERY 0 +#define SVSM_VTPM_CMD 1 + #ifdef CONFIG_AMD_MEM_ENCRYPT extern u8 snp_vmpl; @@ -481,6 +485,8 @@ void snp_msg_free(struct snp_msg_desc *mdesc); int snp_send_guest_request(struct snp_msg_desc *mdesc, struct snp_guest_req *req, struct snp_guest_request_ioctl *rio); +int snp_svsm_vtpm_send_command(u8 *buffer); + void __init snp_secure_tsc_prepare(void); void __init snp_secure_tsc_init(void); @@ -524,6 +530,7 @@ static inline struct snp_msg_desc *snp_msg_alloc(void) { return NULL; } static inline void snp_msg_free(struct snp_msg_desc *mdesc) { } static inline int snp_send_guest_request(struct snp_msg_desc *mdesc, struct snp_guest_req *req, struct snp_guest_request_ioctl *rio) { return -ENODEV; } +static inline int snp_svsm_vtpm_send_command(u8 *buffer) { return -ENODEV; } static inline void __init snp_secure_tsc_prepare(void) { } static inline void __init snp_secure_tsc_init(void) { }